Are there mountains near your home? If there are, where did they come from? How do mountains get to be so tall compared to the surrounding land?
Most mountains are formed in one of two ways: through the action of plate tectonics or because of volcanic action.
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Plate tectonics animation from http://www.ucmp.berkeley.edu/
The number in the lower right represents millions of years ago. |
Plate tectonics. Scientists believe that some mountains were formed because of the movement of the huge plates that make up the Earth's crust. The term 'plate tectonics' describes this theory. It says that the Earth's crust is covered by a number of rigid plates that float on molten rock under the Earth's surface. As the plates slowly move, they sometimes collide. These collisions can cause earthquakes. The collisions can also cause large pieces of rock, or even part of the plate, to tower up into the air. This process can form mountains.
Scientists believe that the mountains in our mystery country were formed this way. Long ago, two large plates crashed into each other, causing a chain of mountains to be pushed up.
Volcanic action. Sometimes the Earth's plates do not push up themselves to form mountains. Instead, their movement causes magma to push between the cracks and be erupted into the air. Magma is nothing more than molten rock. When it cools in the air after erupting, it becomes rock again. After many eruptions, there will be a mountain formed from the cooled magma.
Last year's Great Toy Challenge destination, El Salvador, has many volcanoes. And there are many other places around the world with active volcanoes. People who live in Oregon state in the US, for example, were quite surprised when their own volcano, Mt. St. Helens (see photo), erupted 22 years ago. That eruption blew the top of the mountain completely off, and spread ash across several states.
The mystery country for this year's Great Toy Challenge is not known to have any volcanoes. Does that give you a clue?
Learn more about the mountains nearest your home. Were they formed by volcanic action, by plate tectonics, or in some other way? Are there any active volcanoes nearby? If yes, when was the last volcanic eruption?
Check out past Trade Topics entries!
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